Posted 09 February 2013 - 11:24 AM
She has no reason to distrust him. She only remembers him as the boy he was. She hasn't seen him since she married Ned and moved to Winterfell so she has no idea of his double dealings and plotting in KL. She has good reason to hate the Lannisters because of Lysa's letter, Bran being pushed out the window, the attempt on his life after Ned had been made Hand of the King. Obviously she's not going to believe anything the Lannisters tell her and Littlefinger is devious in his plots and schemes. He's not going to announce his plots to the world now is he? If Ned and Cat had spent time in KL over the years maybe it might have been a different story as they would have heard and seen things at close quarters and have a better idea about all the power plays in KL.